From time to time, the network generates "imprint blocks" which contain two peices of info: A and B. A is either a common public key from which addresses can be matched, or a bitcoin address. B is the balance in that address.

At that point clients need only download in reverse to the most recent imprint block, unless they wish to obtain transaction history.

This is really what I see as the fundamental flaw in the bitcoin protocol, all transaction history is available, forever. With this new method the only important peice of info is the last imprint block. These blocks could even be produced daily if bitcoin took over the world.

Imprint blocks are as secure as the blockchain itself and would be signed (and sign future blocks) in the same way.

Since old addresses would always be carried forward there would no longer be a need to scan the blockchain. These imprint blocks could even be produced nightly by the devteam and included with new clients. Imagine the lightning fast startup times beginners would experience.